Speed Limits Reduced in Hamilton County to Improve Air Quality
Truck speeds will be reduced to 55 mph by early summer

Nashville, Tennesse - The Tennessee Department of Transportation (TDOT) announced today that the department is agreeing to a request made by the Mayor of Chattanooga and the Mayor of Hamilton County to reduce the speed limit to 55 miles per hour for commercial trucks in Hamilton County in order to reduce polluting vehicle emissions with the goal of bringing Chattanooga and Hamilton County back into federally required ozone attainment levels as mandated by the Early Action Compact. The Early Action Compact is an Environmental Protection Agency program based on early action by local and state governments to reduce emissions in advance of regulatory deadlines.

“After studying the issue we believe that lowering the speed limit for large trucks will make a difference in air quality for Hamilton County,” said TDOT Commissioner Gerald Nicely. “A study conducted by the Federal Highway Administration shows that reducing truck speed limits by 10 miles per hour can reduce the nitrogen oxide (NOx) emission factor by approximately 18% or more per truck. If we get reductions anywhere close to that level in Hamilton County it will be worth it.”

Nicely said new speed limit signs will be in place and the new 55 mph regulation should take effect by early summer. Nicely also said the speed limit for automobiles will be reduced simultaneously to a maximum of 65 mph on interstates and controlled access highways from a maximum of 70 mph in Hamilton County. “The reason for reducing the speed of cars as well as trucks is to lessen the difference between the rates at which the two types of vehicles will be traveling.”

"We are grateful to Commissioner Nicely and TDOT for working with us so closely to lower truck speed limits in Hamilton County," said Chattanooga Mayor Bob Corker. "This action not only makes the air cleaner for our citizens. It helps ensure that we meet all of the requirements of the federal Early Action Compact as well as to maintain our robust efforts to attract new good paying jobs to the city."

Hamilton County Mayor Claude Ramsey partnered with Mayor Corker in making the initial request to TDOT. “We really believe this can make a difference in air quality. This is not just about official regulations; this is an important health issue. We appreciate the commitment we’ve received today from everyone involved in this effort.”

The action is supported by the Tennessee Department of Environment and Conservation which works throughout the state to regulate and improve air quality.

“Reducing truck speed limits is another way citizens and government officials at all levels are working together to ensure our air is healthy to breathe,” said Betsy Child, Commissioner of the Tennessee Department of Environment and Conservation. “Studies show that lowering the speed from 65 to 55 mph will help reduce NOx emissions from trucks traveling through the region. Improving air quality takes every control measure available, and I want to commend Chattanooga’s local leadership for taking this step forward."

The Chattanooga/Hamilton County Air Pollution Control Bureau estimates that reducing truck speeds from 70 mph to 55 mph could have the same impact as eliminating all industrial NOx by 11% in Hamilton County on a daily basis. “The Pollution Control Bureau also estimates that the decrease in speed will add only approximately three minutes of travel time to a truck’s trip through Hamilton County,” Nicely added.

All parties involved agree that the enforcement of the new speed limits will play an important role in the success of the pollution reduction strategy. The Tennessee Highway Patrol will be ready to help, according to the head of that department.

“One of the key components of road safety is travel at safe and reasonable speeds,” said Tennessee Department of Safety Commissioner Fred Phillips. “We have worked closely with TDOT through this decision making process and are in agreement that the speed limit change is beneficial. It is the responsibility of the Department of Safety, through the Tennessee Highway Patrol, to ensure the new speed limit and all other traffic control regulations are followed by motorists.”

Mayor Corker said the city staff is also planning to meet with local law enforcement agencies to discuss the implementation of the new lower speed limits in the coming weeks.

A total of 56.85 miles of interstate will be impacted by the speed limit changes in Hamilton County. A section of US27 that runs approximately 17 miles in length will also have lower speed limits posted.

The University of Tennessee has provided impact information showing the effect of vehicle speeds on emissions which can be seen in the Nashville Early Action Compact report. That report and maps of the impacted area can be viewed by clicking the links below.

• FHWA Emission Reductions Report (PDF)
• Hamilton County Existing Speed Limits (PDF)
• Hamilton County Proposed Speed Limits (PDF)